Photocatalysis relates to the phenomenon of transforming light energy into chemical energy. There are many materials, such as, SrTiO3, ZnO, ZnS, CdS, and TiO2, for example, that are considered to be efficient photocatalysts. TiO2 is characterized by having an energy band gap in the range between 3 and 3.2 eV. Light energy and the electron band gap energy of TiO2 are compatible or equivalent to ensure effective interaction of TiO2 material with UV light. TiO2, as a photo-active material, can therefore, efficiently utilize energy from sunlight and transcend in photocatalyzing chemical reactions. For instance, absorption of a photon by a TiO2 crystal enables excitation of an electron (e−) from the valence band to the conduction band if the photon energy, hν, equals or exceeds the band gap energy of TiO2. Simultaneously, an electron vacancy or a positively charged hole (h+) is generated in the valence band:hν+TiO2→e−+h+The electron-hole pair (e−+h+) that is created migrates to the TiO2 photocatalyst surface triggering redox reactions to take place with compounds adsorbed to the surface of the photo-catalyst and/or in the surrounding medium. For TiO2, photo-generated positive holes have redox potential of ca. 2.5 eV against normal hydrogen electrode (NHE), this potential allows production of hydroxyl radicals from water. Whereas, the redox potential of photo-generated electrons (−0.52 eV) is capable of reducing oxygen O2 to superoxide (O2−) or hydrogen peroxide (H2O2). Hence, there are sufficient redox potentials to initiate a chain of redox reactions that can lead to decomposition of most organic molecules.
Thus, because of its inherent photoactivity, TiO2 can be an efficient photocatalyst. A need exists, however, for a photocatalyst that can adsorb and decompose organic molecules and/or environmental pollutants. In particular, a need exists for a substrate that can be used with TiO2 to provide a photocatalyst that can efficiently adsorb and decompose organic molecules and/or environmental pollutants. Furthermore, a need exists for an economical and environmentally friendly technique for producing such a substrate.